U.S. Pat. No. 4,082,229 discloses a waste disposal unit operated entirely by water from a domestic water supply. A piston moving in a toroidal chamber and driven by water pressure is coupled to a stack of alternately moving and stationary cutters. The moving cutters have a reciprocating rotary motion and are provided with staggered interfitting teeth which reduce waste material progressively to small particles. The lowermost cutter has restricted openings which will not pass any large particles, or silverware or the like which may accidentally fall into the unit.
A servo controlled valve, responsive to differential pressure on opposite sides of the piston, reverses the water flow and the piston direction automatically at each end of a stroke. The automatic reversal also occurs if an obstruction jams the cutters, the cutters then oscillating with a reduced stroke until the obstruction is cut off or removed.
The driving water is exhausted through the valve into a manifold from where it is sprayed into the cutting chamber to flush waste material through the cutters.
The device described in Pat. No. 4,082,229 is a very efficient device that requires effective sealing and the minimizing of cross leakage between the channels and passages which conduct the water for the operation of the waste disposal unit. It is also desirable that the device by constructed and arranged so that the cycle time for rotation of the cutters is as short as possible.